16.5 (b) December 24, Christmas Day, and December 26 shall be off-days for all
purposes, including travel, and no Club may request a Player’s consent to practice on such days
for any reason, provided, however, if December 26 falls on a Saturday and the League has
scheduled NHL Games on such date, December 23 may be substituted as an off-day for all
purposes, including travel, instead of December 26.

The team says they waited till midnight to fly (which is passive aggressive enough in itself):

A published report says Flyers violated the CBA by traveling to Nashville at 8:24 pm Dec. 26; Flyers told me they flew at midnight. Hmmm